In recent years, hybridmagnetic levitation motors of the double-bias permanent magnet type have been proposed as magnetic levitation motors.
The five-axis control type hybridmagnetic bearing disclosed in Patent Document 1 is intended to magnetically levitate the major axis rotor and to rotate it highly efficiently under five-axis control by using a bias magnetic flux generation permanent magnet. The magnetic paths are changed so that a magnetic suspension force greater than that of a magnetic levitation system that only uses an electromagnet is generated.
According to Patent Document 2, double-bias type magnetic bearing (suspension control) succeeds in generating a greater magnetic suspension force by using a plurality of bias magnets of a conventional hybrid magnetic bearing. Also, a hybrid magnetic bearing with greater power is realized by inducting the magnetic flux of the secondary bias permanent magnet by using the primary bias permanent magnet.
However, when the technique of Patent Document 1 is used for a pump or the like, the configuration of the inlets and the outlets of the pump becomes complicated because there are salient poles at both ends of the rotor for controlling the axis directional position, which makes the assembly difficult. Also, as the channel for liquid becomes complicated, there is a great loss in sucking and discharging.
Also, in the technique of Patent Document 2, the polarities of the salient poles arranged in the circumferential direction of the magnetic bearing change alternately from S to N and from N to S. Accordingly, an eddy current is caused as the rotor rotates so that the loss of the rotor's rotation becomes great, which is problematic.    Patent Document 1    Japanese Patent Application Publication No. 2006-14528    Patent Document 2    Japanese Patent Application Publication No. 2007-120635